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Cat brains shrank in size as a result of domestication

A new study led by the University of Vienna has found that, as cats became domesticated over the past 10,000 years, their brains have shrunk significantly in size. According to the scientists, the discovery adds further evidence to what is known as “the domestication syndrome” hypothesis.

This theory argues that natural selection for tameness in domestication leads to the production of fewer neural crest cells in the animals’ brains. Neural crest cells are linked to fear and excitability and their reduction likely contributes to changes in brain size, stress responses, and overall body morphology.

The scientists compared the cranium sizes of domestic cats (Felis catus) and several species of wild cats from Africa and Europe that are genetically related to the ancestral species that domestic cats have been evolving from over the past millennia. They found that domestic cats, as well as hybrids of wild and domestic cats, have smaller craniums (and thus brains) than their wild counterparts.

“Our data indicates that domestic cats indeed, have smaller cranial volumes (implying smaller brains) relative to both European wildcats (Felis silvestris) and the wild ancestors of domestic cats, the African wildcats (Felis lybica), verifying older results. We further found that hybrids of domestic cats and European wildcats have cranial volumes that cluster between those of the two parent species,” reported the study authors.

According to the researchers, the main reason behind the reduction in brain size is the fact that domestic cats lead an easier life, in more comfortable surroundings, while facing significantly less threats and risks from predators.

Earlier studies have also shown similar reduction in brain size in other domesticated mammals, such as dogs or rabbits, compared to their wild ancestors. 

Even human brains appear to have shrunk over the past 28,000 years, being currently five percent smaller than those of Neanderthals. Experts suggest that the gradual change from hunter gatherers, who needed to face a wide range of threats during their peregrinations, to sedentary farmers leading more peaceful lives may have contributed to this reduction in brain size.

The study is published in the journal Royal Society Open Science. 

By Andrei Ionescu, Staff Writer

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